8/23/2011

You DON'T need CPUAffinity, nBackup, shadow and multifile databases

Right now at www.firebirdnew.org you can see the survey about Firebird features in production environment.

Some answers look like dangerous signals, especially for those who run big Firebird databases.

So, what's wrong with these answers?

1. CPUAffinity. CPUAffinity can be used to bind Firebird SuperServer to some particular CPU/core. At present we have plenty of cores even at desktop workstations, so there is no reason to use SuperServer and limit Firebird to the only CPU - use SuperClassic or Classic architectures to run Firebird at full throttle.

2. NBackup. In IBSurgeon we do not recommend our clients to use NBackup without external monitoring and as the only way of backup. NBackup makes the straight copy of database on page level - it's fast, but, unlike the gbak, it does not check pages' contents. If you use only NBackup and does not perform necessary database maintenance (at least regular sweep, combined with transaction markers monitoring), and someday your database became corrupted (due to RAM problem or abnormal shutdown, for example) , NBackup will continue to make (and overwrite) "backups". Another danger is "frozen: delta-file, when database are not unlocked correctly, and all changes are written to delta-file, and cannot be merged due to delta file problem. To use nbackup strengths and avoid pitfalls, we setup special backup scheme for our clients.

3. Shadow is completely useless in modern production environments. It provides protection from the only type of corruption - occasional critical crash of HDD (assuming that shadow is configured correctly, with 2 separate HDDs). Use RAID5 (or RAID10) instead - it will be much faster and more convenient for maintenance.

4. Multifile database. There is no actual reason to use multi-file database at present. With multi-file it will be impossible to do NBackup, database files will be tied to its locations, and it will give no advantage at all. Often multi-file databases are being implemented to perform copying of database to DVD, but you need to switch off Firebird during this operation.

Summary

Of course, the title of this post is a provocation, and sometimes administrator need to use CPUAffinity, nbackup and other features (not shadow!), in order to achieve some specific result, but it should be done correctly and with full understanding of steps to be done. NBackup is the most useful tool, which is very often understimated both in terms of strengths and possible problems with it.